master: Add storing quota entries in metadata

This commit adds new section in metadata called 'QUOT 1.1' to avoid conflicts
with previous quota implementation. QuotaDatabase needs to add methods of
dropping all database and inserting limits stored in QuotaEntry.
For storing in metadata, template functions fs_{store,load}_generic() are
invented and used for quotas' case.

Change-Id: I16c361743c09145d32dded085dce2e741c3b2b7c
master,metarestore: Support quotas in changelog

Store log entries for SETQUOTA operations and replay the operations
during recovery.

Change-Id: Ibd1a58ff5237ddff89bec5c9a41357fc0a8cc213
tests: Add setting quotas to tests of metadata

Add setting some quotas in test_metadata_dump and test_metadata_recovery
to verify if SETQUOTA entries in changelogs are handled properly and if
quotas are properly saved into metadata files and loaded from them.

Change-Id: Iabab11a215b643ed04e72b63dd8a99028154bbfa